In its 20th-anniversary year, “Pokémon” is more popular than ever. Nintendo released the “Pokken Tournament” fighting game in March to favorable reviews. “Pokémon Go” struck like a bolt of lightning, becoming a global phenomenon. And for the past 11 months, fans have been celebrating the series by downloading mythical pocket monsters from the franchise’s history onto their Nintendo 3DS.

The culmination of the celebration is the release of “Pokémon Sun” and “Pokémon Moon,” which incorporate changes the series has needed for years. Finally, “Pokémon” has broken out of the mold that defined it ever since the beginning.

In “Sun” and “Moon,” players create an 11-year-old avatar from Kanto who moves to the Alola archipelago, which is loosely based on Hawaii. As the protagonist adjusts to life in these islands, Professor Kukui takes him or her under his wing. “Sun” and “Moon” start off similarly, with Hala, the kahuna of Melemele Island, offering the hero the choice of a starter Pokemon — Litten, Rowlet or Popplio. And from that point, the adventure takes an entirely new turn.

Litten is one of the starter pokemon that players choose from in “Pokemon Sun” and “Pokemon Moon.” (Nintendo)

Gone are the gyms and bosses battled by players in the older games. They’ve been replaced by an island challenge — a rite of passage in which participants go through trials on Alola’s four islands and defeat the totem pokémon on each leg of the journey. Trial captains both serve as mentors and partner with powerful boss pokémon.

“Sun” and “Moon” have a serial structure akin to a series such as “Lost,” rather than the formulaic segments of the earlier games. Players no longer level up their pokémon and challenge gyms. Instead, the interlocking narratives of the new titles reflect the culture of Alola.

The developer, Game Freak, had been working toward the new structure for ages. And it has stirred various save-the-world storylines into the main quest — to become a pokémon champion.

Without the gym structure, “Sun” and “Moon” weave a tale linking the hero’s island-challenge journey to the mysterious Aether Foundation and its connection to inter-dimensional pokémon known as Ultra Beasts.

In “Pokemon Sun” and “Pokemon Moon” gone are the battles with gyms and bosses. Instead, players advance through a series of trials in which they must defeat a powerful totem pokemon. (Nintendo)

The new games’ revamped visuals drop the isometric perspective used ever since the original Game Boy title. As a result, “Sun” and “Moon” look more like modern Japanese role-playing games. And with nothing boxy, the environment seems more organic and lush.

As with the earlier “Pokémon” games, the developer has again introduced a new combat twist. In the previous title, certain pokémon could hold a special stone that reacted with a hero’s bracelet to give the creature super-powers. But in Alola, the focus is on move sets and special pokémon battle actions.

The pinnacle is the Z-move, which is similar to Mega Evolution. A special crystal enables the pokémon to activate the Z-Move, and most of these crystals are tied to pokémon types, and handed out as rewards when a trial is completed. Some are synced to specific species of pokémon. Z-moves can be used just once in a battle, and so a player must figure out the best time to activate that ability.

Litten battles the Alolan version of Raichu in “Pokemon Sun” and “Pokemon Moon.” (Nintendo)

The changes are all significant improvements, and “Sun” and “Moon” feature plenty of lesser changes that upgrade the quality of gameplay. Together, the changes make for a great “Pokémon” experience.

Over the years, “Pokémon” added so many elements that the games felt bloated. The new iteration pares down the elements so they’re accessible, but no longer problematic.

Poke Pelago is a centralized site where players can plant berries, collect beans and care for pocket monsters. Game Freak also has supplied players with a Ride Pager. A player who needs to surf across a waterway no longer has to carry a pokémon with that ability. Instead, he or she can call, and ride, a Lapras, saving hours of time.

The many upgrades make “Pokémon Sun” and “Pokémon Moon” cohesive while dropping the anachronistic elements so that players can focus on the main goal — catching them all.

There are a bunch of cool concerts and comedy shows scheduled for Dec. 31 in the San Francisco, Oakland, San Jose areas, including dates with Primus, Cracker, Camper Van Beethoven, Goapele, Dave Attell, Maceo Parker and Lucius.